Four-dimensional unitarity can be used to obtain stringent constraints on the data obtained thus far. As we now review, these constraints include lower bounds on \(k_{\mathfrak {g}} \) , as well as upper and lower bounds on \(c_{{\mathrm {2d}}}\)  [1]}, [2]}. Beginning with the former, unitarity demands that
\(k_{\mathfrak {g}} \ge \widetilde{k}_{\mathfrak {g}}~,\) 
